21. Gene analysis for spikelet sterility of F1 hybrid between cultivars Silewah and Hayakogane

Tsuyoshi INUKAI1, Masahiko MAEKAWA1, and Noboru SHINBASHI2

1) Agricultural Experimental Farm, Hokkaido University, Sapporo, 060 Japan

2) Hokkaido Green-Bio Institute, Naganuma, 069-13 Japan

An Indonesian variety, Silewah was reported to show a high cold resistance and F1 fertilities with Japonica rices (Satake and Toriyama 1979). However, Ikehashi and Araki (1984) reported partial F1 sterilities between Silewah and Japonica as well as Indica varieties. We found that the F1 hybrid between Silewah and Hayakogane, a Hokkaido variety, was highly sterile although its pollen fertility was normal and that the spikelet sterility was caused by anther indehiscence (Maekawa et al. 1991).

To analyse genes for this sterility, an F2 population from Hayakogane/Silewah (1988) and a B1F1 population of Hayakogane/Silewah//Hayakogane (1989) were tested in a vinyl-house at Sapporo and spikelet fertility was observed. Both populations showed segregation for fertility although the distribution was continuous (Table 1). In view of the pattern of fertility variations observed in segregating populations and variety Silewah (lower than normal possibly due to some environmental factors), plants showing fertilities higher than 65% in 1988 and higher than 75% in 1989 may be taken as fertile and those lower as sterile. Thus, the segregation pattern in F2 is regarded as 9 sterile: 7 fertile and that in B1F1 as 1: 1. This suggests that a set of complementary dominant genes controls the nondehiscence of anthers, although the penetrance of the genes can be lowered by modifiers in segregating populations. Our tentative gene model is that the interaction of genes A and B brings about non-dehiscence, and that Silewah has AAbb and Hayakogane has aaBB. These genes may be designated by S-A(t) and S-B(t), respectively.

Furthermore, a triple cross, Hayakogane/Silewah//Norin 20 was observed (Table 1). The segregation pattern was judged to be 1 sterile: 3 fertile. This is explained by assuming the genotype of Norin 20 be aabb or s-A/s-A(t) s-B/s-B(t). Sterility of hybrids between normal parents is always due to interaction of parental genes. But, complemetary genes causing sterility do not seem to have been reported in the past.

Table 1. Distributions of spikelet fertility observed in F1, F2 and other
cross populations involving varieties Hayakogane, Silewah and Norin 20
===============================================================================
Parent and cross Generation    Spikelet fertility, (%)     No. of  Ratio  X2  
                            ============================== plants
                             5 15 25 35 45 55 65 75 85 95
===============================================================================
1988 experiment
Hayakogane(H)                                        1  5     6 
Silewah(S)                                  1  2  1  2        6 
H/S                F1        3                                3
H/S                F2       57  4  4  5  6  9 14 19 31 61   165    9:7    1.50
                            _________________ ___________
                                    85          80

1989   experiment
Hayakogane(H)                                          12    12
Silewah (S)                                       5  5       10
Norin 20(N)                                       2  8  2    12
H/S                F1        6                                6
N/S                F1                             1  2  2     5
H/N                F1                          2  1  5  6    14
H/S//H             B1F1     31 18  5  6  3  4  6 15 24 33   145    1:1    0.01
                            ____________________ ________
                                     73            72

H/S//N                             1  4  4  6  4 14 33 32    98    1:3    1.65
                                   _____________ ________
                                      19            79
===============================================================================
All chi-square values are non-significant.

 

References

Ikehashi, H. and H. Araki, 1984. Varietal screening of compatibility types revealed in F1 hybrids of distant crosses in rice. Jpn. J. Breed. 34: 304-313.

Maekawa, M., T. Inukai and N. Shinbashi, 1991. Spikelet fertility in F1 hybrids bteween rice varieties Silewah and Hayakogane. Jpn. J. Breed. 41: 359-363.

Satake, T. and K. Toriyama, 1979. Two extremely cool-tolerant varieties. Intern. Rice Res. Newsl. 4: 9-10.